With the advent of homebuilt setup of femtosecond time-resolved photoelectron imaging, Prof. Zhang Bing’s group has studied the dynamics of excited states in o-xylene molecule. The ultrafast internal conversion from the S2 state to the vibrationally hot S1 state on timescale of 60 fs is observed on real time, as shown in Fig. 1. In addition, the ‘channel three’effect is observed in the S1 state of o-xylene. The secondarily populated high vibronic S1 state deactivates further to the S0 state on timescale of 9.85 ps. The lifetime of the low vibronic S1 state is much longer, extrapolated to ~12.7 ns. The lifetime of the S1 state depends strongly on the vibronic excess energy. The great differences of lifetime of different vibronic S1 state are due to their different radiationless dynamics.

This work has been published in Optics Express (2010 , 18 (6)：5791-5801), and the reviewer commented that this is an interesting paper with exciting results.